Method of preparing 2-methyl-4-hydroxy-5-alkoxy-methyl-pyrimidine



Patented July 25, 1950 METHDD OF PREPARING 2-METHYL-4-HY- DROXY-S -ALKOXY-METHYLPYRIMIDINE Gustav A. Stein, Plainfield, N. J., and Joseph R. Stevens, Easton, Pa., assignors to Merck & 00., Inc, Rahway, N. J a corporation of New Jersey No Drawing. Application April 10, 1946, Serial No. 661,086

This invention is concerned generally with novel processes for preparing intermediates useful in the synthesis of vitamin B1. More particularly it relates to an improved method for the manufacture of Z-methyl-4 -hydroxy-5-alkoxy-methyl-pyrimid ine.

Vitamin B1 is known to be 4-methyl-5 phydroxye'thyl-N [2-,methyll-amino-pyrimidyl- -(5)-methyll thiazolium chloride hydrochloride which can be represented by the followingstructural formula:

ride. The ethyl-fl-ethoxy-propionate can be prepared according to one prior art process by.

reacting ethyl acrylate with metallic sodium in ethyl alcohol solution. The overall process possesses various disadvantages, namely: (1) the process is a three-step process involving the preparation of ethyl-,S-ethoxy-propionate, reaction of this compound with ethyl formate, and reaction of this roduct with acetamidine hydrochloride; (2) the first two steps employ sodium metal which requires special equipment and is hazardous in commercial operation;- (3) the process requires isolation and purification of the intermediate ethyl-c-ethoxy-propionate. This purification step is necessary since it has been found that when crude ethyl-c-ethoxy-propionate is employed it interferes in subsequent operations and that a poor yield and low quality pyrimidine derivative results. Thepurification requires costly distillation columns containing a large number of equivalent theoretical plates in order to separate the ethyl-c-ethoxy-propionate from the undesirable contaminating materials;

furthermore, due to the possibility of decompositlon,'it is preferred to conduct this fractionation 6 Claims. (Cl. 260-251) carry out under plant conditions and one likely to be attended by considerable losses of. product. In View of these diificulties, the overall yield from ethyl acrylate .according to prior art processes has always been limited to about 30% of'theory.

The present invention is concerned with 1 a novel process which can be carried out in a single reaction vessel without isolation. of intermediate product, whereby a Z-methyI- l-hydroxy-5-alkoxymethyl-pyrimidine is prepared from an acrylic acid ester in yields of about 50% of that theoretically obtainable. In this process an acrylic acid ester is condensed with a formic acid ester and an alkali metal alcoholate, andthe crude product (which contains a-metallo-formyl- B-alkoxy-propionic ester) is reacted directly without isolation with acetamidine hydrochloride. I

In carrying out the process according tothe present invention, a mixture of an acrylic" acid ester such as ethyl acrylate, methyl acrylate, phenyl acrylate, benzyl acrylate and the like, is reacted with a formic acid ester such as ethyl formate, methyl formate, propyl formate, phenyl formate, benzyl formate, and the like, and an alkali metal alcoholate, such as sodium ethylate, sodium methylate, potassium ethylate and the like. The alkali metal alcoholate can'bep'repared, if desired, in the same reaction vesselby reacting the appropriate alkali metal with an allphatic alcohol, but it ispresently preferred'to use technical sodium ethylate. The reaction can be conducted between the components alone or in the presence of a hydrocarbon diluentwhich is a non-solvent for the starting materials and products such as petrolatum, benzene, toluene, xylene, solvent naphtha and the like. Any temperature below about 40 can be employed but applicants prefer using a temperature of about 30-35 C. The reaction is conveniently controlled by adding the mixture of formic ester and acrylic ester with stirring and over a period of about 1 hour to the slurry of alkali metal alcoholate in a diluent; the mixture is then allowed to stir chemically represented, in the case of applicants preferred process, employing ethyl acrylatelethyl formate-and sodium ethylate, as follows:

The crude product obtained in the abovere'action can be reacted directly with acetamidine hydrochloride to produce the corresponding pyrimidine derivative. This condensation is best conducted in aqueous solution and in the absence of oxygen at below about 15 (3., preferably at about 5 C. The temperature is conveniently regulated by adding the acetamidine hydrochloride dissolvedin ice water solution portionwise and with cooling-toxthe crude. a-SOdiO-fOXHlYl-flalkoxy-propionic ester reaction product. The reaction mixture should preferably be protected from oxidation which can be accomplished by maintaining an atmosphere of nitrogen :or: other inert gas above the batch in the reaction vessel. In order to obtain maximum overa1I- conversion of the acrylic acid ester toithepyrimidine compound, it has been found best to use an excess of each of the other reactants; in the .casepf the acetamidine, an amount approximately equivalent to the acrylic acid ester originally employed is first added in aqueous solution and themixture allowed to react for about 1 hour; the aqueous .layer, containing the 2+methyl 4-hydroxy-5- talkoxyemethylepyrimidine is then separated and Lam-additional :equivalentoi .iacetamidine hydro- ;chloride is" added together-with suflicient sodium .ihydroxide ptozneutralize :the hydrochloric acid acon-tent and-the resulting solution is allowed to react at abouti0-5 Cuiorran additional 24 hours. Therpyrimidine derivative is recovered from this -;solution by. anysconvenientsmethod; forexample .by'extracting thei'impurities withether, then adfiusting iwithxaceticacidto"a pH of approximately diaand .then extracting the desired 2-;methyl-4- rhydroxy-B-alkoxy-methyI-pyrimidine therein vby .means of a:solvent;such aschloroform, ethylene adichloridencarb'on disulfide, and the like. This reaction-may" betchemically represented,.: in the case of applicants preferred process, employing ac sodioeformylfi ethoxy-propionate and .aoetl'am-idinerhydrochloride, :as follows:

0 HONa NH :The 'following .examples. illustrate method-soot marrying .outthe presentrinventiombut it is to rbe understood thatithey aregiven-bywaylofiillusetrationeand not-of limitation.

Example 1 About 6'? ;g.: of sodium ethylate islsuspendedtin about-400- cc. petrolatum'and'a mixtureot-about gof ethyl acryl-ate and '74 g. of :ethyl-tormate .isadded thereto with-stirring over approximately sa l hour period and at aztemperaturecfi about .-30-35-- C. The mixture which contains rCtSCd'iQ- zformylefi-ethoxy-ethyl-propionate -:is cooled "to about 0-5" C. and-to this mixture is added-.- under :an atmosphere of nitrogen, a solution containing :about48 g. of acetamidine hydrochloride, .dissolved inabout 124 goofice water. The mixture stirred .for approximately .1 .hour, theaqueous layer is separatedrand to this aqueous solution is added an additional quantity of .about- '58 :g. ;-acetamidine hydrochloride andlaboutl9 g. of

sodium hydroxide The resulting solution .is allowed to stand for approximately 24 hours at about 0-5 G. and is then extracted twice with approximately 50 cc. portions of ether and sumoient acetic acid is added to the aqueous layer to bring the pI-Ltoapproximately 6. This solution isthen extracted repeatedly with chloroform and chloroform extract evaporated to dryness to 4 produce about 52 g. of crude product which corresponds to about 73% theoretical yield. This crude material can be purified if desired by washing with acetone to produce substantially pure 2-methyl-4-hydroxy-5-eth0xy-methyl-py- *rimidiue; ,M. P. 177-178 C. Yield of purified materiali about 48% of .theory.

Example 2 Two experiments were carried out in each of which '50 g. or ethyl acrylate was reacted with 76g. of ethyl formate and 67 g. of sodium ethylate substantially as'described in Example 1 and the product reacted with g. of acetamidine hydrochloride. The aqueous layer was separated from the reaction-mixture and extracted repeatedly .formate and 61 g..of acetamidinehydrochloride.

Thisgave 26g. of acetone-washed 2.-methyl-.4- hydroxy-5-ethoxy-methylpyrimidine. (M-"rP. -17?- 178 0.).

It is thus seen that the yield byour improved method is between-40' and60% higher than that obtainable by the, prior art process.

Modifications'may be made in carrying out the present invention without departing from the spirit and scope thereof andthe inventionz is to belimited only by-theappended claims.

-We claim:

l. The process which comprises simultaneously -reactirig an a'crylic ester; an alkyl iormate and an alkali metal alcoholate to produce a' reaction product-containing the corresponding 11- (-me'ta'll'oformyD -13-alkoxy'-propionic ester; and bond-ensing said reaction productwithout separation with acompound selectedfrem the-class which -con sists of acetain-idineand salts thereof'to produce pyrimidine. 4

2. The process-lwhich comprises simultaneously reacting .:=ethyl racrylate, ethyl formate an d sodium ethylaterto produceza reaction-product :containingethyl .a- ,(sodio-formyl): -.;9-ethoxy-pro.- pionate land, condensing .said. ,reaction :product without separation :with -acetamidinehydrochloride to ;;pro.duce .2emethylA-hydroxy-ethoxy methylepyrimidine.

v3. The process which{compriseszsimultaneously reacting ethyl acrylate, ethyl formats, and sodium ethylateto produce a reaction product containing ethyl .a-' (sodioeformyl) -,6-ethoxy-propionate .addingacid-to form ethyl.a-formyhfl-ethmqmmo- .pionate;.and condensing said aneutralized reaotion product .withoutseparation with acetamidineeto produce Z-methyliehydroxyed-ethoxy-methyl- .nyrimidine.

.4. The processwhichcomprises simultaneously reacting, at a temperature of approximately 30- 35 0., a mixture containing an acrylic ester, an alkyl formate and an alkali metal alcoholate, said reaction being carried out by adding a mixture of acrylic ester and formic ester to a suspension of alkali metal alcoholate in a hydrocarbon diluent, to produce a reaction product containing the corresponding a-(metallo-formyl) -fi-a1koxypropionic ester; and then condensing said reaction mixture at a temperature of about 0-5" C.

' with a compound selected from the class which consists of acetamidine and salts thereof to produce Z-methyl-4-hydroxy-5-alkoxy-methyl-pyrimidine. I

5. The process which comprises simultaneously reacting a mixture containing an acrylic ester, an alkyl formate and an alkali metal alcoholate, said reaction being carried out by adding a mixture of acrylic ester and formic ester to a suspension of alkali metal alcoholate in a hydrocarbon diluent to produce a reaction product containing the corresponding a-(metallo-formyD-fi-alkoxy-propionic ester, and condensing said reaction product without separation with a compound selected from the class which consists of acetamidine and salts thereof to produce 2-methyl-4-hydroxy-5-alkoxymethyl-pyrimidine.

6. The process which comprises simultaneously reacting, at a temperature of approximately Bil-35 C., a mixture containing ethyl acrylate,

ethyl formate, and sodium ethylate, said reaction being carried out by adding a mixture of ethyl acrylate and ethyl formate to a suspension of sodium ethylate in petrolatum, to produce a reaction product containing ethyl a-(SOdiO-fOIIIlYD- fi-ethoxy-propionate, and condensing said reaction product without separation, at a temperature of about 0-5 0., with acetamidine hydrochloride to produce 2-methyl-4-hydroxy-5-ethoxymethylpyrimidine.

GUSTAV A. STEIN.

JOSEPH R. STEVENS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,328,595 Williams et a1 Sept. 7, 1943 2,332,896 DAlelio Oct. 26, 1943 FOREIGN PATENTS Number Country Date 554,324 Great Britain June 29, 1943 OTHER REFERENCES Koelsch, Jour. American Chem. Soc, vol. 65. 1943, pp. 437-439. 

1. THE PROCESS WHICH COMPRISES SIMULTANEOUSLY REACTING AN ACRYLIC ESTER, AN ALKYL FORMATE, AND AN ALKALI METAL ALCOHOLATE TO PRODUCE A REACTION PRODUCT CONTAINING THE CORRESPONDING A-(METALLOFORMYL)-B-ALKOXY-PROPIONIC ESTER; AND CONDENSING SAID REACTION PRODUCT WITHOUT SEPARATION WITH A COMPOUND SELECTED FROM THE CLASS WHICH CONSISTS OF ACETAMIDINE AND SALTS THEREOF TO PRODUCE 2 - METHYL - 4 - HYDROXY - 5 - ALKOXY - METHYLPYRIMIDINE. 